docs: def authenticate_nova_user(self, keystone, user, password, tenant):
          """Authenticates a regular user with nova-api."""
          self.log.debug('Authenticating nova user ({})...'.format(user))
          ep = keystone.service_catalog.url_for(service_type='identity',
                                                interface='publicURL')
          if keystone.session:
              return nova_client.Client(NOVA_CLIENT_VERSION,
                                        session=keystone.session,
                                        auth_url=ep)
          elif novaclient.__version__[0] >= "7":
              return nova_client.Client(NOVA_CLIENT_VERSION,
                                        username=user, password=password,
                                        project_name=tenant, auth_url=ep)
          else:
              return nova_client.Client(NOVA_CLIENT_VERSION,
                                        username=user, api_key=password,
                                        project_id=tenant, auth_url=ep)